Combustion control device for solefired horizontal coke ovens



June 2, 1953 C, Hum-EES 2,640,805

' COMBUSTION CONTROL DEVIC FOR SOLE-FIRED HORIZONTAL COKE OVENS FiledMarch 16, 1950 11 Sheets-Sheet 1` A/EY geg-@ June 2, 1953 c. H. HUGHES2,640,805

COMBUSTION CONTROL DEVICE FOR SOLE-FIRED HORIZONTAL COKE OVENS FiledMarch 16, 1950 1l Sheets-Sheet 2 ff/ /f//f/ f/ 4 /I JNVENTOR.CHARLESHHUQHES June 2, 1953 c. H. HUGHES 2,640,805

OOMBUSTION CONTROL DEVICE FOR SOLE-FIREO HORIZONTAL COKE OVENS FY/9"?"INVENTUR.

CHARLEsf/.HL/ws Ar U June 2, 1953 C, H. HUGHES 2,640,805

. COMBUSTION CONTROL DEVICE FOR sOLE-FIRED HORIZONTAL COKE OVENS F'iledMarch 16, `195o 11 sheets-*sneu 5` .57 INVENroR.

@HARLEBAHL/qf/Es "YQ June 2, 1953 v c. H. HUGHES 2,640,805

COMBUSTION CONTROL DEVICE FOR SOLE-FIRED Y HORIZONTAL COKE OVENS FiledMarch 16, 1950 11 Sheets-Sheet 6 INVENToR. :HA RL E5: H140 L7/455'Arran/Vey 11 sheets-sheet- 7 INVENTOR CHARLES- Huug/IES BY@ @W ATTORNEY.

June 2, 1953 c. H. HUGHES COMBUSTION CONTROL DEVICE FOR SOLE.FIREDHORIZONTAL COKE OVENS Filed Maroh 16, 1950 5 0 0 4 2 D E R I J m O sm RSWW E o Hmm www D Hmm N OI c NH o T.- T s U B M O C 3 5 9 l 2, e m JFiled Mann lea,` 195o 11 Sheets-Sheet 8 INVENTOR.

E E H G U um H. u.. L R A H E om .mi ...om N:

BY G.

TGS

ATTORNEY.

11 Sheets-Sheet 9 ATTORNEY um mm3". :.Spomau .f 2a .mund uzku:

C. H. HUGHES COMBUSTION CONTROL DEVICE FOR SOLE-FIRED HORIZONTAL COKEOVENS E L m H E June 2, 1953 Filed March 1e, 195o m-.. LTT

mTQ* June 2, 1953 HORIZONTAL COKE OVENS 11 sheets-sheet 1o Filed March1e, 195o Y E N R O T T A..

June 2, 1953 C, ||l HUGHES 2,640,805

COMBUSTION CONTROL DEVICE FOR SOLE- EIRED HORIZONTAL COKE OvENs Fi1edMarch 16, 195o 11 sheets-sheet 11 BY C @y ATTORNEY..

Patented June 2, 1953 Lear oFF-Ice C'OMBUSTIONiGKONTROL"DEVICE-FOR SOLE-F1RED=HORIZGNTAL `COKE OVENSr Charles-H. 'HughesGlen Ridge, N.` J.,`assigner toiHugvlresrByg-lProduct Coke Oven Corporation;

New-York, N z'A Yi, a. corporation of New Yorkkv Application-Marchil,1950, Seri'al'No' 150,052:

The present invention relates tothe. art ofibroad coke ovens, and.more-:.particularlyto..amimf proved method of operating a broad.- cokeoven and to the -pyrolytic .treatmentin .a broad coking oven` ofstraight chainA hydrocarbons, such.. as paraffin hydrocarbons.occurring. in. petroleum andthe like, to Aconvert themintouaromaticlihy.- drocarbons, suclras benzol; toluoLxyloljnaphthalene, anthracene; landthelike, While evolving vapors containing.straight'. chain .hydrocarbons from a fluid-.hydrocarbon .mass.-and.carbon-izing the residue thereof intoandmproved carbonized product, `and toanimprovedlbroad coke Aoven provided .with vfa,..recircuation .flue andadapted to produce saidcarbonized,productl.

I-Ieretofore,y various .methods have. been. used for the operation ofbroadcoke ovensland forthe conversion of hydrocarbons,.particularlyoflth'e straight chain type, into otherhydrocarbon .reacvtion products,particularly ofthe-aromaticorring fluid hydrocarbon masses, and the poorquality and lovv` grade of .the aromatichydrocarbonsand coke which Wereproduced. In.,.attempts..at actual commercial operations of thepyrolyticconversion of hydrocarbons, the. results obtained were so poor. that theoperations were disconu tinuedxand were givenfupn as commercially.inadvisableor as industrial failures. Although various endeavors weremade to overcome.. the foregoing fdiiiiculties, none, as faras Iamaware, has

been Wholly satisfactory for commercialoperation conducted -on a full.industrial scale.

The present invention involves the. discovery that in crackinghydrocarbon vaporsv evolved vduring the coking of .petroleum residue,for instance, for the production of aromatic hydrocarbons, it

is .necessary to. control not only the direction. `of

rflovv of the vaporsand.thetemperatureoflthe yield.

It is. anotherobject of the invention to .provide an .improved 'method ior the cracking of straight chain. .hydrocarbons and Ytl'ie'irconversioniinto aromatic hydrocarbons vvithal .sufcientlyhigh yield toWarrent industrial operation.

A further objectof the invention is to provide lytic treatment oftheevolved vapors contain-ingv straight `chain hydrocarbonsandtheir'conver'- sion into aromatic hydrocarbons. Itis also Within thecontemplation offthe'invention tof provide. a new -and* improvedlIrlethod involving the use of a broad sole fired colting'oven in whichtar and carbonv resulting ,fromithe pyrolytic treatment of hydrocarbonscan'V be made into ahigh carbon coke .'havinga true specific gravity oftwo or more; andespleciallyI suitable for the manufacture of carbonelectrodes: It is still'a further o-bjectof the inventionto provide. .animprovedy method using'a cracking and coking oven of novel and" improveddesign providing a heating system for the distillation'of heavypetroleum, tar ofthe like and "also `a--separate heatingsystemWithinthe'sa'me oven stru-cture for thecrackin'g of the-'oilvapors'andthe .is maintained.

pyrolysis of paraffins for the production of aromatic oils and otheraromatic hydrocarbons.

It is also an object of the invention to provide an improved methodinvolving the use of a broad cracking and coking oven having the wallsof the vapor flues constructed with uneven surfaces to produceturbulence of the oil vapors in such a manner as to cause the oil vaporsto contact the hot wall surfaces, whereby effective pyrolyt'ic treatmentof hydrocarbons can be conducted.

Moreover, it is an object of the invention to provide a novel processemploying a broad coking oven involving novel and improved combinationsin which an increased and positive control of the flow and velocity ofthe oil vapors through the vapor flues is maintained, and in whichpositive control of the air to be preheated is provided, together withpositiveY control of the waste gas from the oven, the said combinationsinvolving an arrangement of structural elements which are capable ofcausing the air being heated to flow through horizontally-'disposedrecuperator tubes and of causing the waste gas which is being cooled toflow around`the recuperator tubes, whereby uniformity of unidi-`rectional flow and an effective change of temperature is imparted tothe air from the sensible heat in the waste gases.

Furthermore, it is an object of the invention L'to provide an improvedprocess utilizing a broad coking oven having a multiplicity of straight,independent heating flues extending parallel to the oven and divided onthe center line of the oven,

so that the heating iiues connect on each side of 'the center line of.the oven with two separate re- 'cuperators thus providing for acontinuous vstream of the heating gases throughout the wholel heatingsystem from each flueburner `to 'the'l ,recuperators and the stack.

' 'The invention likewise contemplates the'pro- 'vision of a uniqueprocess using an oven structure in which novel recirculation flues areemployed below each floor heating nue for the recirculation of the wastehot gases from each Vmultiplicity of burners and heatingflues underconstant and uniform temperaturewithout having to reverse the ow ofthewaste gases, through vstructural means for preheating the air and forrecirculation of hot gases through the heat- Aing flues whereby aunidirectional flow of gases A further object of the invention is theprovision of a novel process involving the charging of petroleum coke oflow specic gravity into the oven and raising the floor temperature toproduce a high temperature in the green coke to coke. Y

The invention further contemplates a novel .combination of operationsinvolving the charging of coking coal or other suitable solidcarbonaceous material into the new oven and producing either domestic ormetallurgical coke.

Still another object of the invention is to provide a unique processusing an improved oven construction for the production of coke and thecracking of hydrocarbon oils, in which cracking flues are so locatedthat a separate long heating flue is directly below and parallel to eachindividual cracking flue, and in which each oil vapor cracking flue issupplied with an air jet for the purpose of burning out any carbon whichmight collect in each oil vapor ue.

It is also within 'the contemplation of the invention to provide animproved broad coke oven having a recirculation nue combinationincorporated therein whereby substantially uniform heating can beproduced within the oven without overheating in the oven floor adjacentto the burners and underheating at the center or within central areas ofthe floor.

With these and other objects in view, the invention comprises thevarious features, operav tions and combinations hereinafter more fullydescribed and more particularly defined in the annexed claims.

The novel process can be carried into practice in the improved solefired 4broad coke oven which is illustrated in the accompanyingdrawings, in which:

Fig. 1 is a vertical longitudinal sectional view showing a broadcoking-oven, tubular recupera-- tors, upper heating flues, lower heatingflues, waste gas recirculation lues and other ilues in which the oil `orother hydrocarbon vapors are cracked, gas manifolds, and piping totheupper and lowerv longitudinal heating' systems, waste gas outlets and`cracked Yoil vapor off-takes;V

Fig. 2'illustrates a'vertical cross-sectional view .of a broad, cokeoven showing the vertical recuperators lower heating system, waste gasrecirculation iiues, `upper heating nues, flue s in which the oil vaporsare cracked, the/air supply tothe recuperators, and the air Aand oilports leading into the oven;l f

Fig. 3 depicts avertical cross-sectional view taken on the section line3-3 of Fig. 1, in which the iiow of air isindicated through the tubularrecuperators by means of arrows, and the flowof oil or other hydrocarbonvapors directly from the oven to the vapor off-take is also indicatedbymeans, of arrows;A f. Fig. j4 is. a vertical cross-sectional View takenon thesection line 4-4 ,of Fig. 1, in which the travel ofthe waste gasesfrom the lower heating system intotherecuperator is indicated;

Fig. 5 shows an end kview of the oven from the right in Fig. 1, takenfrom thesection line 5-5, showing the gas piping to the lower and gasand airpiping to the upper heating systern, and air pipe connections tothe vapor cracking hues;

Fig. 6.is a horizontal sectional view of the recuperators takenon thesection line -e of Fig. 1, in which the flow of waste gas and incomingair is indicated by arrows; l Fig. ldepicts a horizontal sectionalviewtaken on the section line 'If- 1 of'Fig. 1, in which the flow of wastegas into the recuperators is indicated by arrows; l y

Fig. 8 is a horizontal sectional view taken on the section line 8 -8 ofFig. l, showing the flues connecting the air nues from the recuperatorswith thev lower heating flues;

Fig. 9 illustrates a horizontal sectional View taken on the section line3 9 of Fig. 1, showing i Fig.; l0- .-isa horizontal-r sectional:viewztalren on x-the'sect-ion line; 1I il-i-Itl of` Fig.. 1fdirectly-belowthe yiioorf` of: ithe:V` ovenf-` and'` showing.; theflower heating -:flues;

:-Fig; 11--depicts-,a-horizontal sectional View taken .on'the;..sectionline II-ri lof Fig: 1, `showing-the longitudinal fiues r of ftheupper-,heatingsystem directly below the .-oor of the oil .vaporcrackingiflues;

Fig. 12 shows. a horizontal. sectional viewtalren on-the section line:l.2--.l 2 of Fig.; 1, showing the oilA vapor cracking sflues extendinglongitudinally of the oven, the View showing in detail: their- .regularsurfaces of the cra-cking flues;

"-'Fig., 13 `illustrates a diagramma-tic perspective zview offmyx-novel; oven clearly showingithe flow of gas, air, -fu'el,.steam,-.oil-.or tar,--etc.,-rtherein;

Figs:1 llV and 15 l. are Avert-ical ,longitudinal sectionralviews of a.modified embodimentof 'the present invention. showing f recirculationvflues combined with heating.Y flues and an. arch-supported; down-draft;.hot .waste gas, vertical ducts connected to recuperators;

Fig.' 16 --is a fragmentary, sectional view-ofthe supporting. archoverythe down-draft; het waste gas, vertical ducts .shown :in fFigs;l4-.andi15;l

lFig;v 17y -`vdepicts -a sectional view taken .on. vthe 'line I'l-I'IofFig. 16;

lFigs. 18l andl 19 :are-enlarged, fragmentary views, vpartly.-insection, of .the recirculation' flue systems illustrated in Fig: land'Fig; 14, respec- `tively;

iFig. 20'illustrates-a diagrammatic plan v-iew `showing the-'iflow ofairV and gases through the recupera-tors and-associated f-ues; etc. and

AFig. 21 is a diagrammatic perspectivesviewof my novel oven clearlyshowingl the :new of gas, air; and fuel; in such-.amanner-as toillustrate the required continuous unidirectional stream yof Vtheheating gases throughout the wholeheatfing system from each iiueburnerto: the 'recuperators and the stack.

--Broadly-istated; the present invention'contemplates the operationofaLAbroad-coke cven in -a novel manner aswell as'thepyrolytic conversion ofhydrocarbons-for the production of y aromatic hydrocarbons-suchasbenzol;-t'oluol,\-xylol and Y`the like, by the-heat treatmentofpetroleum resi- I-duesor other hydrocarbon oils, tars; or materials-to-' produce l'iydroca-rbonv vapors --or gases in the--manner-.hereinafter more fiilly--set-Fforth. HIn accordance with theinvention an improved broad coke oven is provided including anovenstructure and cracking'chambers oruesfin which the pyrolyticconversion can be controlled-within a temperature rangek to effectthe'desi-red--con- Version.

-By controlling the direction of `flowofthe hy- -drocarbon vapors vinthe oven andl through the cracking chamber, and-by controlling thetemperatures in the cracking chamber, whileat the same time controllingthe space-velocity and -tur- =bulence of the 'vaporsp relativelyhigh-'yieldsof aromatic hydrocarbons can be obtained. In carrying theforegoing operation into-practice,-large -quantities of Jgases areproduced'f-rom-the-pe- -troleum-residue--or the like undertreat-mentp-as 'well as 'tar andcarbon'which are converted linto All of,the foregoing operations areI useful coke. conducted-within a `singlerefractory-structure having 'a novel combination of.; cooperating ele--ments by which' improved results are obtained,

"the". Wastefxgas recirculation-ities, :sin which: the

now; of the wasteY gas-Eto: the preheated. airaflues is indieatedrbyarrows;

tpl

Very: anda-separation .of

;.e1i.minating-z certainoperating difficulties:- cfg-.prioroperations-and: substantially reducing-` .the :cost

of,manu-factureoff -thezproducts obtained t relay.

-A high- -yield-:Yof-,aromatichydrocarbons; andfithe production; offvelectrode -coke can --be obtandby Jthe;processing-.off-about Llfgdegreeto aboutgl/z degree API .residuum oil, -fo-rex-ample;-bychargingA the:-oil'into' A'they oven atabout '709 ?F.;-,and f cracking,the,hydrocarbonvapors-producedv there- 'fromat a temperature-ofabout1.350:2-F., fforin- .stanca-inthe cracking chambergor cracking-'fineshereinafter described-and the subsequent recov- .componentsj-offthe-.reaction-produced. i

Thesingle novel structure or apparatus employed in carrying-out `thepyrolytic conversion-:of -the hydrocarbons-includesa broad cracking.`and coking i oven.`v whi'ch,-in a commercial' installation can be about42 feetflong-and-Uabout10%f'feet wide; being rectangular Aat `thebase-ofthe oven and arched `in the manner shown vmorepart-icularlyinfFig. 2 ofv the :drawings-which isf-combined-With aheating system adapted tooperate witlr either rich -fuel gas; such` ascoke.oven-gas,

oil gas, or with liquidA fuels, such as fuel oils, tars, and the like,land whichcan' be combined-with preheated air` from recuperatorsand-miXed with recirculated -hot waste-gases. Housed---Within-'theupperfpartof the-oven structure-isa-cracking chamber provided-with anindependent-heating systemwhich can beso controlled as -to-obtain thedesiredl temperature in the "floor andside walls` of the oil-crackingflues.` The entire brick work structure ispreferably-encased--in-avmetal shell, such as a welded steel casing, whereby the interior of theoven-may be operated under-pressure or under sub-atmosphericpressure,1asy desired. l

VGenerallyspeaking, the oven heating-'system -below-the-oven Iioorpreferably consists vof any suitable number of f nues, depending -uponthe oven width employed, the'iiues being preferably arrangedlongitudinally of 'the ovento-support and heat the 'floor thereof.`llachglongitudinal `-fiueis preferably-divided at its ltransversecenter line: so that the Waste gas'f-romeachhalf flue is diverted intothe'recuperators situa-ted below and parallel to the-corresponding halfof the oven. The two sets ofhorizontal -recuperators' located A-b'elowand-parallel to the oven and to the heating fluesare in constant-useduring the operation oftheV apparatus to supply heated air to oppositeends ofthe `floorheating finesv and to constantly ,receivethe hot wasteproducts of combustion ywhichj-in turn,- pass totheY oven waste-gasstack.

.chamber O-l 'through charging ports P-l ,ini-both 'sides oi thexsidewalls of the oven. The oil vapors pass from' the coking chamber .O.-|"through 'damper-controlled off-take ductsD, air-both sides of ftheoven, intov a topiplenum chamberP-Land thence throughfducts D i,eontr-olledhy dampers D-T, intof'vapor` heat-treating flues 'VF-I,andout of the voverrstructure` through breechingB-l and jwsh-pu vane"mL-'1mm' a' vapor flue 'Vj-3 to a conventional or standard by-productrecovery apparatus well known to 'those skilled inthe art.

At the beginning of the distillation process, for

a period of perhaps ten to twenty minutes, it is fde'sirableV to takevoffthe Vuncracked heavy oil vapors/through a duct D-2 (see'Figf 3) ai;each yside of the oven, the ducts'being provided with dampersD-S whichcontrol the passage `of the vapors into' the vaporbreeching B-l. Theflow `ortravelof the-oil vapors at the start of the oven voperation canbe controlled by closing the dampers D-4 (see Fig. 2) in 'both of theducts Dy the dampers D-3 (see Fig. 3) in both ofthe ducts -D-'Zbeing'open, thus permitting the vapors to flovv'directly to thebreeching B-I, through the wash-oil valve VV-2, to the' vapor main V-3,and from thence to the by-product recovery apparatus. `After the floorof the oven is covered with .the hydrocarbon oil or tar to .be treated,and Acoking-has started, dampers D-l in both of the `ductsD maybe'opened, and the dampers D-3 in air by 'meansfof' oven doors OD-Lprovided at the coke pusher end (see left end in Fig. 1) and also at thecoke discharge end of the oven.

Beneath each half of the broad coking chamber O-l (see the left andright halves, referring to Fig. 1) and running parallel to the lengththereof are heating iiues I, 2, 3, 4, 5, G, 1, 8, and 9 (see the lefthalf of Fig. l, and Fig. 3) and I-F, Z-F,

right half of Fig. 1 and Fig. 2), which are preferably arrangedhorizontally, and each half flue is preferably independent of theadjoining ues. The ilues are separated from each other by longitudinalpartition walls as is indicated in Figs. 2 and 3 of the drawings. Theheating flues Al to 9 (Fig. 3) and I-F to 9-F (Fig. 2) are provided atthe outer ends thereof with suitable heating means, such as gas burnersB2 and B-3 (see 1), which can be lsupplied with fuel in a manner to behereinafter described. Below each floor heating flue is a recirculationflue RC, for the recirculation of hot waste gases from and to each floorheating flue, so as to produce, during the operation of the apparatus, along flame and to provide uniform heating of the oven oor.

Below the recirculation lues RC on each half of the oven are located twosets of recuperators R-l Rf-2, and lit-3, R-4, the recuperators R-l andBP2 being in series, and Rf-3 and R4 being also in series, but the twosets in series operate indepently of each other, as will be apparentfrom the detailed description of the operation of the apparatushereinafter more fully set forth. The tubes of the recuperators arepreferably constructed of silicon carbide, which permits a very rapidand almost instantaneous transfer of the sensible heat from the hotwaste gas through the wall of the tubes to the air to be preheated.

The recuperator R-3 is connected with the floor heating fiues l to 9,inclusive, through ducts D-S (see Fig. l), 'and the recuperator R-I isconnected with the floor heating hues -F to 9-F. inclusive, throughducts D-6 (see Fig. l). The recuperators R-Z and R-ll are connected withthe waste gas flue C-I' (see Fig. l and Fig. 4).

It will be understood that the portion of the oven heretofore describedin detail relates'ftoth'e lowerhalf of the oven'unit; which isusedprmarily for the distillation of the hydrocarbon oil or tar and `forthe coking ofthe residue.' lThe upper portion of the'oven is designedparticularly for the treatment of Voil'vapors from the hydrocarbon oilor tar to effect cracking or the pyrolytic heat treatment of fthehydrocarbon vapors'for the production of aromatic oils or'compounds. Theoven sectionsor parts are designed to be Operated as a single unit', butthe oil vapor cracking iiues VF-I may be closed oi, if desired, by meansof dampers D-4 (see Fig.'2)"and the oven may then be operated solely'asa' distillation and 'coking oven for the production of coke yand high B.t. u. oil gas.

The heat-treating ues VF-I (see Figs. 1, 2, 4, and 12) which may consistof any desired number of flue's,` asmay be required to handle the volumeand velocity of the oil vapors produced, are preferably arrangedhorizontally, or in a horizontal position longitudinally of the oven,and may be separated from each other by longitudinally arranged'siliconcarbide partition walls W (see Fig. 12), each of which has amultiplicity of projections T which serve to cause turbulence of the oilvapors during passage of the vapors in contact therewith and to producemore intimate contact with the wall surfaces. f

Each duct D-l is' preferably provided with regulating dampers D-'l (seeFigs.' 1 and 2) for the-'purpose of controlling the volume o-, oilvapors from the plenum chamber P-2 to each of the vapor cracking fluesVF-I. Each vapor iiue is preferably provided with an air inlet A-l froma manifold A for burning carbon in the cracking iiues. Beneath eachvapor cracking flue, and arranged in a horizontal positionlongitudinally of each vapor flue VF-i, is a heating ue CF-l (see Figs.1, 2, and 1l). These heating fiues CF-l are preferably single and areseparated by partition walls W-I, as shown in Fig. 1l. Each heating nueis preferably provided with a separate gas or oil burner B-4, which maybe supplied with gas or oil from a manifold B. The products ofcombustion from all of the heating flues CF-I discharge into a flue C-2(see Figs. l and 11) and through a stack flue C-3 to a wasteheat boiler,or'to the atmosphere, as desired.

When hydrocarbon vapors from the charge of residue oil or tar have beenevolvedand there are substantially no more vapors to heat-treat in thefines VF-l, and the carbonaceous residue has been-thoroughly coked, thenthe coke product is ready to be pushed from the oven into a standardquenching car or other suitable container.

The recirculation of gases through the apparatus is as follows:

Hot waste gas from the floor heating flues I to 9 inclusive at the leftside of the oven in Fig. l, flows through ducts D-5. then around thesilicon carbide tubes SC in the recuperator R-3, then around the tubesSC in the recuperator R-4 and into the stack flue C-I. Simultaneously,hot Waste gas from the heating ues F-l to F-S, inclusive, at the rightside of the oven in Fig. 1, iiows through the ducts D-G into therecuperator R-l, around the silicon carbide tubes SC therein, thenthrough the passageway at the right into the recuperator R- around thesilicon carbide tubes therein and then into the stack flue C'-I.

The air required for combustion in the floor heating iiues enters theapparatus through the duct A-2 (see Fig. 2) and passes through ductD-8,- from which'itlis distributedv through-.the silicon carbide'tub'esSC in the recuperator R-2', Where r it is preheatedp and then. passesinto the duct or passageway =.D;9 'wand is `distributed therefrom-intothe. silicon carbide tubes; SC of the recuperator RY l wherenthetemperature 'is normallyraised-to about 150095111. -The air thenpassesfrom: the tubesin thereeuperatorR-l `into .the duct"D=Ill-,1 from-whichit .passes into-.duct D .Il (see\Figs..2;and 8) andiromthenceto:ductsD-l 2, thenupward .through ducts D1-1S; then :upward through.thev lateral ducts or :passageways De! d (see'Fig.r 1) intothe heatingnues I 4totinclusive, and :|F. to 'l-F inclusive, underthe .oren floor.

The-.Volume of preheated air toeach loorheat. inglue may be regulatedasdesiredffby means vof dampers-DAE (see-Fig. 1), the airservingrtosupport combustion `of the oilv orfgasburnedbythe burners B-Latthevrightfendfof theoven in Fig. 1, andfB-3 at the :left end of-,theoven,.as shown irr'Fig. 1; Each offthe oilfxburners B-2and'.B-3 is4operated 1 under r steam .pressure I and has. an inspirator action,which not only causes forward flow ofthe preheated air, but also drawsazlarge volume of hot waste gas from eachfloor heating ue throughopenings or ductsCF-Z (see-Fig. 1) into the recirculation ue-.RC andcausesthe hot waste products to niixwith theairfinlthe duct DelliI (seeFigs.. 1 andi?) directly below each burneriB-Z and B-Zl;` At the'innerend of the recirculation fiues are projectionsPF (see-.F'g, 1) whichextend upwardlyginto each` heating flue and serve -to deflect i a.volume `of the v-hotz'waste :gas into each recirculatingfiue-RC.

For the purposeof.giving-those'-skilled yin the` ff art abetterunderstanding of the novel recirculation nues embodyingtheipresentinvention, a detailed description willbe-given in connectionwith the drawings generally andparticularlyinzoonnection with Fig. 1 andFigs.v 13ste 21. As--pointedout 'hereinbeforef thev heatingfluesonly,`extend for vone-half the length ofrthe broad oven which facilitates theattainment and control of substantiallyuniform coking temperaturesthroughout the length ofthe -fioor of-thafoven :and the avoidance -oioverheated -.ends1neary the burners with the production of hot-spots and.burnt or overcolxed coke and vof underheated areas near the center ormiddle ofthe oven with the produc.- tion of coldspots and .-green orundercolredqor underburnt coke. To provide a complete control of thecombustion of the fuel theheatingffluesand of the production anduniiormity.- of.'y heat temperature therein; unique recirculation nuesare arranged in combination ywith f,l1e.-'heat` ingv flues and theheatA.recuperator or heat .eX-'1 change system in a special manner, as will.befullyr described and explained hereinafter.

The structureof one. embodiment yof :the rechi-,-

culation systeniis-iillustrated. in Figs, 1 and 13. A-

detailed enlarged View of the.- construction. is shown in Fig.. 18;. Itwill bexobservedthat 'divided heating. nues are used with-"heating nuesl to'9.

extending for; one-half the length. otrth'efoven from the. left-bandisidey provided with= burners B-.Sto approximately-the center or middleof.:the-

oven and. With heating ues1l-F to, 37E exten-ding for the othernhalfofrthe-ovenwfrornxethe: right-A hand side to approximately the ,centerJor-.middlec A lbridge wall BW vextends from. theoVen'floorito.

a supporting: arch SRiinxthe-recuperator struc tureA ancl'divides therightihand heatingffues from the left-hand heating.: luesi. Underneatheach divided or half Avheating..-flue .is alrecircu'lar. tion --ue: RC.As 'may l be 5seen fromithef. drawings;y particularly fromfgFig..p18,.each recirculation flue is connected.` at both ends toitscooperating:or :superimposed heatingi'ilue locatedl direct-fv ltr-above.- In theembodiment shown;I eachv recirculation; :flue :is heat v ezichaneerelation with its cooperating onzsuperirnposed. heating-flue and is4preferably separated-.ionlyv'by a singleref-rac.-tony"tilewhich-'constitutes the bottom of the heating uefandithetop ofthe recirculation flue (seeFig.;,2)i. At .theouterends oieachrecircula-V tiorrfiue adjacent toltherig'ht and-,left-hand sides ofth'etnewfovenf, connectionnis madeiwith a hot air conduit por :fine:which conducts the preheated frcrniafrecuperatorto-the burners at I.theends et the.. heati1ig';;flues fand; which permits for :en: ables themergingacf the-streamer hot burnt gases beinssfrecirculated rw-iththe-preheated air. By so. doingigjthe iiainerom theburnersislengthene-duarifiv,theuvelocitypof-lame propagation is reduced.- Inthis. mania-ter, substantially g uniform heatings provided yoversubstantially the entire oven-a i'loor` for; sul@etantiallvY-i the-entirelength tlnereoi,l thereby .avoidingoverheated ends of the oveniand.underheated centers-or central areas. Some of ythe burnt gases`from. .the combustionA of fuel inlthe heatingfluessiswithdrawn via ,aport PT.; which: is adjacent the bridge walll and wh-ichois,VY iny,connection with outletducts .l1-5 leadingto the. recuperators..

In the modified -zembodirnent of `thevinvention illustrated in Fig. 14,the oonheating filles l to 9 fanueJFAr tofQF-and recirculation flues RCserve thefsamepurpose as that heretofore describedfor flueswitl'il--thef same. reference; numerals, as illus:V trated inpFig. 1.A111 important difference, however, is that Fig.4 v1 shows the hot wastegas from the. door heating nues flowing downwardly through twoverticalluesDjand D-l which dividathe flowpf thevgasesinto twol streams-flow,ing through.upper horizontal .tubular recuperators Rf-I and R-S, thenthrough tubular recupera.- tors .R712 .and .-Rel,4 `and finally. intoone. chimney il-ue C-.i to. the.waste gas stack, whereasFig. 14onli/providesY Onevertical Waste. gas flue D-5. The. purpose ;of thespecial construction of the modied-embodimentis .to insure control ofthetemperature of., the. air. to r.be vpreheated. through' the` tubes.in.\tubu1ar recuperators T -l, T-2, and 'Ila-3. on,.the .rightside ofr,the centerline vof.the oven andthrough tubes. in tubular recuperatorsT7-4,..T.-5,; andTfS. on the left side of the center line ottheoyen and,tothe` burners..v The pref heated.l air` from the recuperator tubesenters ainducts-.A-.. and A-.l2. (see-Figs. 14 and 20), andpassesthroughvertical lues HA to theheating nues.y The volume ofhotairto the heating nue. burners. is. regulated .by Ameans of dampersHD...and^IID-2.,in. verticalflues HA. The` other structural vfeatures of.thamodied oven .are ese sentially thesame asthose illustrated vin Fig.,1 and described heretofore,A excepty no cracking chamber. is,-;providedvand `additions. .are made. to thegendsz-of .the recirculation iiluesvto providefor the use fof gas vas-fuel. Thus,.Fg. .14 shows the upper..part of the ovenwithout. cracking lues which are not .required when onlyycoke, uncracked oil .Vaporsfand gases-are produced.. In certain oilren'eries-:thehoperations` are preferably..con.- ductedtocharge Lheavy7petroleum -oil or residue intoy ovens solely `for the production ofrecoverableersf. Under. suchconditions, thecracking'fi'lues canbemttedas clearly illustratedin the modi# f fied designfshownin Fig-314..

accesos 11 In Fig. 15, an arrangement of floor heating flues,recirculation flues, single waste gas flue D-' and tubular recuperatorsT-I, T-2, T-3, T-', T- and T- is identical to the combinationillustrated in Fig. 14. The main difference is in the upper half of theoven and at the ends of the recirculation flues. In the oven illustratedin Fig. 14, the cracking lues have been omitted and the oven is to beused only for making combustible gases, condensible oil vapors and cokefrom oil residue, etc. from about 2 API to about 6 API grade, whereasthe oven shown in Fig. l5 is to be used for calcining green petroleumcoke or for coking coal or other solid carbonaceous material. Thus, Fig.shows the upper part of the oven without the cracking ues but equippedwith charging holes through which green petroleum coke or coal or othersolid carbonaceous material can be charged into the coking chamber.

In certain oil refineries, a large tonnage of petroleurn coke of lowspecic density, high carbon content, and low ash is recovered. This isknown as delayed coker coke and contains from about 10% to about 18% ofvolatile matter and is known as green petroleum coke. Such coke can becharged into the novel broad ovens and calcined to produce a coke with ahigh density (e. g. a real density of 2.{) and is suitable for themanufacture of electrodes for producing metals and alloys, particularlyaluminum andV pardescription of the preferred construction is as iAspace must be providedvertically and hori zontally into vwhich the lowerbrickwork can ex-v pand. The heating flue division walls FW are'supported by arches AR.- The thrustof the arch# es'ARis taken into theskewbacks SKY which are backed up by walls FW which yextend from thesupporting steel plate BP to the underside of the oven floor tile and inno way resting uponA walls BW. The walls BW extend to the top of steel lbottom plates BP which leaves space C between the top of wall BW and thelower side of arch AR.v VIn Figs/17 and 19 the walls BW extend up#wardly'between the arches AR and terminate level with the bottom of theheating ilues. Space CS provides for expansionV ofthe brickwork betweenthe extended walls BW and each side of al1 arches ARI (see Fig. 1)located at the inner end of the recirculation hues. Projectors PF extendupwardly into each heating flue. I

Fig. 18 shows a vertical section through the oven floor heating flues lto 9 and lF to 9F, recirculation ues RC, the two'waste gas lues D-5 andD- connecting the floor heating fines with the tubular recuperators RFI,R-2, R-3, andR-d and burners BF2 and B-3 as in oven illustrated inFig. 1. The volume of preheatedV air to each burner is controlled bysliding damper DiS. The Volume of hot gases being recirculated to eachheating flue adjacent to each burner is controlle by sliding damperD-IE. The purpose-of the recirculation flues is to provide a structurein which by means of inspirating oil or gas burners a large portion ofthe hot waste gases from the oven floor heating flues can berecirculated through and around the flames from the floor burners toreduce the high flame temperature at the burners and at the same time tolengthen the flame by controlling the volume of preheated air to eachburner, as excess air will produce a short, very hot llame near theburner tips. Inspirating burners cause suction and induce a flow of hotwaste gas from the heating nues to flow through openings CF-2 into therecirculation flues RC. The deflection of the hot gas into therecirculation flues is assisted by the projectors PF. The recirculationof the hot waste gases as described and illustrated in the drawings,especially Figs. 1, 13, and 18 through recirculation flues RC is inducedin large volume whenever fuel oil is injected under steam pressurethrough burners B-Z and B-3. Satisfactory results have been obtained byrecirculating a volume of hot burnt gases equal to about one-half of thetotal volume produced. The proportions can be varied in accordance withparticular conditions as those skilled'in the art will readily appre-rciate.

In the' operation of the ovens, as illustrated in Fig` 14 for heattreating heavy oil and in Fig. l5 for calcining green petroleum coke orthe coking of coal or other carbonaceous material, where it is desirableIto use gas for heating the oven oors, the fuel gas injected at moderatepressures does not have sufficient suction action to draw the requiredvolume of hot products of combustion through ports I-IP of therecirculation system (see Figs. 14, l5, and 19) without additionalsuction. Such additional suction can be provided by means of injectingcombustible gas, dry steam, hot air or waste gas into the recirculationflues RC through pipes or inspirators S. By adjusting the suction, avolume of hot burnt gases equal to about one-half of the total volumecan be recirculatecl. As those skilled in the art understand, theforegoing results can be achieved by varying the cross sectional areasof the heating flues, recirculation flues, etc. and by varying thevelocities of the streams of burning fuel and hot burnt gases, thepre-heated air, and the recirculated gases. While the cross sectionalareas of the heating fiues and the recirculation ues are usually aboutthe same, it is preferred to have the area of the latter slightlysmaller, especially when inspirators S are employed.

The regulated flow of hot Waste products is best vdescribed as followsin connection with Figs. 14, l5, and 19: The hot products are induced toow upward from recirculation nues RC through ports HP by the inspiratingaction of the fuel gas from burners B-Z and B-3 where it mixes with hotair from hot air risers HA. The recirculation of the hot gases isfurther induced by the jet action of the dry steam, combustible gas,waste gas or hot air from pipes Sinto the recirculation ilues RC. Thejet action'draws the hot products from' the oven heating ilues throughopening CF-2. The volume of hot products recirculated is regulated byslide dampers D-IS. Projections CF-2 serve to deflect the hot gas intothe openings CF-Z. Broadly stated. the cross sectional areas of thefloor heating flue and the recirculation flue are about square incheseach and about 52 square inches each respectively. With such areas,satisfactory results have been obtained by using gas velocities of about35 linear feet per second for the hot waste products which insures arapid transfer of heat through the sili con carbide floor and whichremoves stagnant films of waste gases from the under surfaceof thefloor. The velocity ofthe recirculated gases is -adjusted-as-fast as canbe obtainedvso as not` to lose much of the sensible heat l.of the Wastehot vproducts before they-are returned-to the burners at the inner endof the noorheating iiues.

In Fig. 19, thearrangement of heating flues and recirculation ues,inspirating burners and waste-gasv de'iiectors PF is identical With-thatillustratedin Fig-18, except for the lsingle Waste` gas flue D-". y

Thelimproved method embodying-the present invention may be carriedoutinanyappropriate oven. For instance, a structure such as -the onedescribed and illustrated in my co-.pending application Serial No.510,760 [now U.'S.1Patent No. 2,410,074] may be used, "but it ispreferred to use the oven describedl and illustrated-'in myparentapplication, Serial No. 597,028 [noW.U. S. Patent No. V2,426,6121. Inthe latter oven having a novel systemof-ol vapor cracking flues locateddirectly. over separate heating. ues .arranged .longitudinally of .thevapor flues and the-oven, the value of. the improved method has beendemonstrated in actualpractice in the cracking and coking ofcarbonaceousl materials, particularly fluid, .plastic or solidhydrocarbon masses,.such as, tar, pitch, heavy residues,oil,.petroleum,.gilsonite, asphalt, hard oil. residues of Aruba(Venezuela), oil-residues, and-acid refinery sludges.

'I'hefollowing is a brief description. of the op.- eration.. of thepreferred .embodiment of my -invention vWhen applied to the-heattreatment of residue oil. known as Dubbs API grawrity heavy residuumoil, for example, for the production of either electrode coke ordomesticvcokeifrom the The oil rapidly ,covers the'v The process can beadvantageously conducted` Y using, for example, a six-houroperatingcycle divided substantially as fol1oWS: The oven can be maintained onstream," that is, With'oil being continuously fed into the oven, duringa period of about four and one-half hours ;..the time required :forcoking is about ve hours, including the time that the oven is onstreamand the time required for pushing the coke from the oven and for lutingor sealing the oven doors and burning the deposited carbon in thecracking ues is about thirty minutes; thus requiring substantially sixhoursA to'- complete fther cycle. The carbon Which'is deposited over thesurfaces'l of the vapor cracking flues :during the cracking Operation isqu-ite fluffyand is readily burned ofiby blowingl air.` -into eachyaporcracking flue lthrough pipes A-`| (see Figs; 1 and 5) during the -'1astthirty minutes of; operation-of the'icycle.: The' coke which isproduced-has a true -specic gravity, asv distinguished from theapparentA specific gravity, of about 2.0, or more, and-mayVcontaiirfrorn up-Y wardsof. about-90 tov-aboutl-Qror 981% or so offixed carbon, together@ with asmallamount of volatile..matter,ll.and.upto-.about 0.5%? ofi'ash." The. .following speciiication'fhasv1beern'satise'd by." my coke:

- oven iioor surface.

of vthe ovenv floor temperature, the gas `to tlie,T

In the poking offany carbonaceous material-,a2

certainpercentageof :fine or small particlesloff coke, known as breeze,isfproduced. This breeze is mixed with the petroleum residue referred tohereinbefore and is coked as previously described. The-product can besold as electrode coke or as a fuel.

The control of the floor temperature of the".

oven is necessary in order tovsatisfactorily regu-f1 late the steps ofthe process from' the point at which the oil, tar, or the like issprayed-over the` In order to maintain control' burners in the heatingilues I to 9,'and `IF to Sill,"

under the floor of the oven is reduced-in volume sc-as to reduce thetemperature of the door from about 20i30o F; to about 1350""11The'tempera'' ture of the oven floor drops. rapidlyas the volume'.

of fuel gas is reduced, and as the oil covers the iioor oi the oven, thevolume .of .fuel gas or4 fuel to the heating flues is increased.Furthermore',y as the depth. ofthe. cokeV yoverthemiioorlpf theoven.increases,morefuel is used-at the-burners to .raise the`.temperatureY las. required-f forv icoki-ng.` the incoming oil which isbeing.,deposited,- vuntil'l at the end of the oil input, when the cokebed is about seven inches thick on the average, then the temperaturev'in the heating flues is raised to van average vofabout 2'7'50cl` F:Awhich visY necessary to complete the cokingvand calciningfofthe oilcarbon residue on the' top surface of the coke.

In the operation of the new broad coking oven, itisrst put` on stream4for anei'ght-hour cycle l and` oil'` is introduced,vpumpedorsprayedonto" the silicon carbide'looriof 'the' oven,"which haslan" initial .temperature Vof-labout 1350" Fl" When'f the oil contactsthe hot door', it is vaporized; By*` continuing the heating, oil'vaporsare evolved andL the residue is carbonized to coke." Although the ovenfloor Vhas-aminimum temperature of about 1350 F.; the oil vapors'have'an'average tempera-l ture oi about 900 F. Duringthe-onistream period,analyses of the oil'vapors were made vfrom samples taken from the ovenchambers at various intervals. The following are the analyses of gassamples taken forty minutes after the start oiv the''eight-#houry cycle'(coliimn"")',`A three hours" after putting "on stream `(column"B)and'siX hours after'the starticolumn'C);:"

Constituent" j"A" lB- Ci' Carbon DioxideKCOg); ercentl' l O. Butyineo.H8) p d0-;-. Lg 8 (1)1 PropylenefCgH) do-... 8. l 2. 7- 6. l Ethylene(02H6) dop--. 9. o 2. 9 e. 7 Hydrogen (H2)..... 0..-. 29.21 51.8 y 44:9arbon Monoxide (CO) 0.... Y. O. 7 0. 6 i 0. 9 Ethan@ gnu) ..do.--. 14.706. 7 6.1' Methane (CHi) ...d0`.... 36:8 34. 3 SB :100. O Y 0 i 100. 0

Specific Gravity... 62.1 34.8 47:5 B. t. u./cu2 ft., Calculated.; l,1134 772` 89l` aeasoe.

sA11 Vof` the gasand oil vapors are drawn or sucked from the oven(seeFig. 1) upwardly in substantially equal regulated volumes throughthe cracking ues VF-l. In the cracking nues, the vapors are cracked byheat emanating from independent auxiliary combustion flues CF-l atregulated and independently controlled Vtempera--` tures which arehigher Ythan those of-the gases leaving the oven and of theupper partofthe oven. These independently Y controlled cracking temperatures areof the order of about 1350 F. tojabo'ut 1400 F. The cracked vapors flowinto a vapor up-take B|, through oil scrubber V-2 and finally intovapororgas main V-3. The analyses of the cracked vapors are as follows:

Table II Weight Constituent Percent Naphthalene cut. Tar

.Timo- V The yields per 1000 cubic feet of cracked vaporV or gas are asfollows:

Table III l:Table 'IV '11', i f

Items Amount l" Tar charged to three ovens V 26,851 Gallons.Gas-produced, M C F S77 M C. F. Taicharged to oven per M C. l?. 30,61Gallons/M C. l. Coke produced 104,000 Pounds. u Coke produced per 110Pounds/M C. F. Light oil produced y.1,428 Gallons. Y K Light oilproduced per M 1.68 Gallons/M C. F. Creosote oil produced 6,610 Gallons.s," Creosote oil produced per MC. F 7.6 Gallons/MYC 4 B. nu; of gas mode(average)... 750 IB. t. u./cu; it. E'ercentweight recovery r 83%;

` Referring nowV moremparticularly to the pro'- duction' ofaromaticjhydrocarbons from the straight chain hydrocarbons evolved inthe oven during the distillation process, it has been. found in actualpractice in a broad oven of my vinvention that the exothermic reactiontemperhydrocarbons to raromatic hydrocarbons. will average about 1350F.,`and that contact ofthe oil vapors with the hot surfaces of thecracking fles/"F-I is required in order to bring about thelconversionyof straight chain"hydrocarbons into aromatic hydrocarbons. To insurecontact of the hot hydrocarbon vapors with thevhot cracking andheat-treating surfaces of the cracking fines, means are provided on ,thesurfaces thereof for causing turbulence of the hot oil vapors. Toprovide for a temperature of about l350 F. to 1400" F. within thecracking nues VF-I, the floor and side Walls of each of the vapor fluesare preferably constructed of silicon carbide in order to attain almostinstantaneous transfer of heat to the oil vapors, and to maintain therequired uniform temperature of the vapor contacting surfaces. It hasbeen found Per M C. F Volume Weight u Lbs.l Copsyltuens Gas PercentPercent API Sp' Gr Gal.

Oven Feed- 8. 4 1. 011 8. 423 Vapor (gas) 0. 6573 Benzol- 0. 857 7. 14Toluol .864 7. 20 Xylol 876 7. 30 LightiNaphth'a 903 7. 522 HeavyNaphtha.. 923 7. 689 Naphthalene cut.. 8. 564 B 9. 795 Coke- Losses:'

Screenings Carbon Burned Water not recovered. Unaccounted or Total..l.L. L.

Inorderto-produce the foregoing yields, average high temperatures of theorder of l400 F.. are required as well as high space velocities andlarge surface contact areas. The new broad oven structure is the onlybroad oven in which the foregoing yields can be obtained.

The yield of about 6.084 gallons of tar per 1000 cubic feet of oil gas,as noted in Table III,

as a result of experiments and tests that it is necessary to cause thehydrocarbon vapors to intimately contact the hot surfaces of the oilcracking flues in order to effect the conversion of straight chainhydrocarbons into the desired aromatic hydrocarbons. The upper heatingsystem heretofore described, including the superimposed vapor crackingnues, has been designerl-v ly incorporated in connection with the ovenstructure of my invention as a means of heating each vapor cracking flueby means of heat radiated into each vapor cracking nue. By means of thestructure as shown and described, turbulence of the oil vapors inpassing through the f oil vapor crackinglues is produced, resulting inature relating to theconversion of straight chain the intimate contactof the oil vapors with the hot Wall surfaces.

Y Fig. 20 is a plan view taken on the line 2li- 2D of Fig. 14 and Fig.15. This figure illustrates the flow of the hot Waste gases from theoven floor heating flues through the tubular recuperators to separateWaste gas stacks as Well as the flow of the air through the siiconcarbide recuperator tubes to the oven floor burners. The waste gas fromheating flues l to 9 and IF to 9F oW downwardly through vertical ue D-5,Fig` 14, Fig. 15, and Fig. 19, to the right around the recuperator tubesT-l, T-2, and T-S to chimney flue G-F to the waste gas stack S. Wastegases also iioW to the left around recuperator tubes T-d, T5, and T-B toWaste gas flue GF-,l to stack ST. The equal ow of waste gas to stack STmay be controlled by means of a mechanical draft ejector WE located inthe stack and valves DW and DW-l as may be clearly seen in Fig. 21. Theair to be preheated enters air inlet A-l and distributing flue A-B (seeFig. 20) from where it flows through all of the recuperator tubes intube assembly T-3, thence to distributing flue A-9, through tubeassembly T-2, distributing flue A-H), through tube assembly T-l, airflue A-l I, air pipe A-I2, risers HA (see Fig. 14 and Fig. 15) to ovenfloor burners B-2.

The air from the atmosphere to be preheated on the left-hand side entersthe distributing flue A-I, tube assembly T-B, flue A-2, tube assemblyT-5, flue A-3, tube assembly T4, flue A-4, flue A-5, and passes tovertical air flues l-IA (Fig. 14 and Fig. 15) and thence to the ovenfloor burners B-3. It isto be noted that the air circulation through thetube assemblies is discharged from tube assemblies T-l and T- which arelocated near hot waste gas iiues D-E thus insuring a high preheat of theair. The volume of the pre-heated air from tube assembly T-l and T-llcan be controlled to either burners B-2 or B-3 by regulating eitherdampers HD-I or HD-2 (see Fig. 21). All of the pre-heated air can beshut off from either the B-2 or B-3 burners by closing damper D. Indaily operation, damper D remains open as Well as dampers HD-I andHIJ-2. In the event that a recuperator assembly has to be shut down,cold air can be supplied to burners B- and B3 through air pipes HA-l andHA-Z.

Whenever an oven is required of small capacity, the novel oven designwill generally be the same except for the Width and length of the oven.In such a case, only one set of recuperator tubes will be required undereach oven and only one stack will be required to handle the Waste gasesfrom the oven heating iiues and the associated recuperator set. Thepreheated air will be distributed to the burners at each side of theoven through flues A-E and A-IZ to risers HA as illustrated in Fig. 20.

Those skilled in the art may obtain a better understanding of the novelmethod embodying theA present invention from the following descriptiontaken in conjunction with Fig. 21. The carbonaceous material, such asoil residue, tar, pitch, coal, etc. is charged into a sealed broadchamber via appropriate means, such as charging holes CH. A thin broadlayer of material having a depth. smaller than its width and a Widthsmaller than its length is formed in said sealed chamber. When fluidmaterialis under treatment, such as oil residue, tar, pitch, etc., it isusually and preferablyl pre-heated to .an`- elevated temperature, 75;

a Valuable coke having properties which make it,

useful for use in metallurgical operations, chemical industries, powerplants, and household stoves, furnaces, etc.

lt has been discovered that a novel combination of operations makes itlpossible to obtain the unique heating effects by utilizing a long hotllame which gives substantially uniform heat throughout the length ofthe heating ilues and the floor of the chamber. The prior artshortcoming of having overheating near the ends of the ovens adjacent tothe burners and underheating around the center of the oven is overcomeby the use of the present invention. The new'results are obtained by theutilization of a continuous, unidirectional iiow of burning gases orfuel,

air, and hot Waste products of combustion and.

of the recirculation of a portion of the hot Waste products through theheating ilues with the incoming pre-heated air and fuel and the burninggases.

Air from the atmosphere is preferably introduced into the heating systemby means of one or more air blowers AB (see Fig. 21). It is preferred tocause the stream or streams of incoming air to flow through a pluralityof tubular recuperators, preferably made of silicon carbide tofacilitate rapid heat transfer and to effect quick pre-heating of saidair. The hot air preheated in the recuperator tubes is lead throughconducting flues to a plurality of burners B-2 associated with heatingflues which are preferably Tests have demonstrated that satisfactoryresults are secured by` of the longitudinal type.

using half heating fluesy which extend from one end to about the centerof the sealed chamber or oven. By so doing, the heating system is di-lvided into a right-hand section and a left-hand section as is clearlyseen from Fig. 21. Thus, air from air blower AB goes through nues A-7andv A-B to recuperator tubes T-3, flue A-9, reci'iperator tubes T-2, ueA-l vand recuperator tubes` T-l, iue A-ll to hot air duct A-I2 to airrisers' HA to burners B-Z for combustion in heating ilues I-F to S-FlThe hot Waste gases or products of combustion flow through the heatingilues into Waste gas duct D-5 around the outside of the recuperatortubes T-l, T-2, and T-3 to waste'gas flue G-F to stack ST. With thecontinuous, unidirectional, flow of burning gases, lair, and hot' A andA-l, recuperator tubes T-B, flue A-2, recuperator tubes T-5, flue A-3,recuperator tubes- T-4 and flue A-ll to 4hot air duct A-5 and risers HAto a plurality of burners B-3 for combustion of fuel in heating flues Ito 9.

7. IN A METHOD OF COKING CARBONACEOUS MATERIAL INVOLVING SEALING IN ABROAD COKING OVEN A CHARGE OF CARBONACEOUS MATERIAL AS A FLAT,HORIZONTAL LAYER HAVING A SUBSTANTIAL WIDTH GREATER THAN ITS LOW DEPTHAND SMALLER THAN ITS EXTENDED LENGTH, ESTABLISHING A PLURALITY OF MAINSTREAMS OF HOT BURNING FUEL IN HEATING FLUES BENEATH THE CHARGE OFCARBONACEOUS MATERIAL FROM EACH END OF SAID OVEN AND EXTENDINGLONGITUDINALLY ABOUT ONE-HALF OF THE LENGTH OF SAID CHARGE FROM EACHSIDE TO A CENTRAL REGION TO FORM STREAMS OF HOT WASTE GASES, HEATINGSAID CHARGE WITH SAID MAIN STREAMS TO COKE THE CARBONACEOUS MATERIALTHEREIN SUBSTANTIALLY UNIFORMLY THROUGHOUT THE SAME AND TO DISTILLVOLATILE HYDROCARBONS THEREFROM AS HOT VAPORS, CONDUCTING SAID MAINSTREAMS TOWARDS THE CENTRAL REGION OF THE CHARGE, REMOVING SAID STREAMSOF HOT WASTE GASES AFTER HEATING THE CHARGE TO ABOUT THE CENTRAL REGIONTHEREOF AND AWAY THEREFROM IN A DOWNWARD DIRECTION SUBSTANTIALLYPERPENDICULAR TO THE SAID HORIZONTAL LAYER, MERGING SAID DOWNWARDLYFLOWING STREAMS OF HOT GASES AS A STACK STREAM GOING TO A STACK, ANDCONTINUOUSLY EFFECTING RECUPERATION OF HEAT BETWEEN SAID STACK STREAMAND INCOMING AIR TO PRODUCE A STREAM OF PREHEATED AIR TO SUPPORT THECOMBUSTION OF SAID HOT BURNING FUEL THAT IMPROVEMENT WHICH COMPRISESPOSITIVELY DIVERTING A SELECTED LOWER PART OF SAID MAIN STREAMS NEAR THESAID CENTRAL REGION TO PROVIDE HOT GASES FOR STREAMS FOR RECIRCULATION,RETURNING SAID STREAMS FOR RECIRCULATION TOWARDS THE ENDS OF THE OVENWHILE TRANSMITTING HEAT THERETO FROM THE MAIN STREAMS THROUGH ASEPARATING WALL OF SILICON CARBIDE, INJECTING A FLUID OF THE GROUPCONSISTING OF COMBUSTIBLE GAS STEAM, HOT AIR, AND WASTE GAS THROUGH ANINSPIRATOR TO ASSIST IN RETURNING SAID STREAMS FOR RECIRCULATION TOWARDSTHE ENDS OF THE OVEN, AND MERGING SAID RECIRCULATED STREAMS WITH SAIDMAIN STREAMS TO CONTROL THE COMBUSTION OF THE BURNING FUEL AND TOLENGTHEN THE FLAMES THEREOF WHEREBY SUBSTANTIALLY UNIFORM HEAT ISSUPPLIED TO SAID CHARGE AND OVERHEATED ENDS AND UNDERHEATED CENTERS INSAID CHARGE ARE AVOIDED.